1. Field of the Invention
The present invention relates to a machine tool with a rest apparatus supporting a workpiece and machining method with the machine tool with the rest apparatus, especially the machine tool with the rest apparatus supporting the workpiece steadily during machining or temporary before and after a holding of the workpiece by a spindle head and a tail stock.
2. Description of the Related Art
It is well known that there are several machine tools with rest apparatuses, for example disclosed in laid-open patent publications of Tokkaihei 11-33892 and Tokkai 2005-262342.
A prior machine tool with the rest apparatus disclosed in former laid-open patent publication has a pair of rest apparatuses movably along an axial direction of a workpiece to achieve high rigidity for supporting the workpiece and to have a flexibility corresponding to any workpieces. Another prior machine tool with the rest apparatus disclosed in latter laid-open patent publication has a fixed rest apparatus and a spindle head and a tail stock movable along an axial direction of the workpiece to achieve improved supporting force or supporting rigidity of the workpiece by the rest apparatus.
Generally speaking, a rest apparatus is positioned closer to a machining position than a spindle head or a tail stock is so that the rest apparatus should receive larger machining or grinding force than the spindle head or the tail stock does. Therefore, supporting rigidity of the workpiece by the rest apparatus affects to machining accuracy greatly. The fixed rest apparatus disclosed in the latter laid-open publication has larger supporting rigidity than that of movable rest apparatus disclosed in the former laid-open publication.
The machine tool with the rest apparatus disclosed in the former laid-open publication has the flexibility, however, it does not change a relative position between a pair of supporting positions because the pair of supporting positions are constructed as one unit of a body. Therefore, it is not applied for cutting a plurality of supported portions of the workpiece those which supported positions are different from that of the other workpiece. The machine tool with the rest apparatus disclosed in the latter laid-open publication does not disclose any technologies to support a plurality of kinds of workpieces selectively.
The other prior machine tool with a rest apparatus is disclosed in a laid-open patent publication of Tokkaihei 9-123039 that includes the rest apparatus having a weight supporter supporting a weight portion of the workpiece and a journal supporter supporting a journal portion of the workpiece.
The machine tool with the rest apparatus disclosed in the last mentioned laid-open patent publication has to change the rest apparatus in accordance with another kind of workpiece. Therefore, an operator should change manually the rest apparatus, needing a lot of manpowers for machining the plural workpieces.